Field of the Invention
The present invention relates to a colorimetric value acquisition method, an image forming device, and a colorimetric value acquisition control program, and particularly relates to a colorimetric value acquisition method, an image forming device, and a colorimetric value acquisition control program for acquiring a colorimetric value to correct a flare level of a chart simply and properly.
Description of the Related Art
In a device such as a scanner or a printer, a device value (an RGB value or a CMYK value) output from the device depends on the device, and therefore a color conversion table (device profile) to convert this device value into a color not depending on the device is created, and color conversion is performed using the device profile.
Regarding creation of such a device profile, for example, when a scanner profile is created, the scanner profile can be created by measuring a chart for creating a scanner profile output from a printer with a scanner and a colorimetric apparatus and correlating an RGB value measured with the scanner with a colorimetric value such as an L*a*b* value of a CIE 1976 color space or an XYZ value of a CIE 1931 color space measured with the colorimetric apparatus. When a printer profile is created, the printer profile can be created by measuring a chart for creating a printer profile with a scanner and acquiring a colorimetric value from an RGB value measured with the scanner using the scanner profile.
When an RGB value is acquired using the chart for creating a scanner profile or the chart for creating a printer profile, it is necessary to detect only reflected light from a patch to be measured. However, actually, in addition to the reflected light from the patch to be measured, an output including reflected light from a surrounding patch is acquired due to irregular reflection. Such a phenomenon that reflected light more than an original output is measured due to irregular reflection between a measurement object and a light source is referred to as a flare. When an RGB value is acquired, it is necessary to correct an influence by the flare.
Regarding a technology for correcting this influence by a flare, for example, JP 2003-283773 A discloses a flare correction data measuring method using an irradiation unit for irradiating a reading surface of a document placed on a document placement surface with light, an imaging unit for imaging the reading surface with light with which the reading surface of the document is irradiated, and an image reading device for forming image signal data from a signal output from the imaging unit. In the flare correction data measuring method, a point light source is disposed on a measurement document a reading surface of which is formed of a diffusion reflected surface, light reflected by the entire reading surface is imaged by light emitted by the point light source, image signal intensity distribution data divided into image regions including light emitting image regions of the point light source as basic units is generated from a signal output from the imaging unit, and flare correction data is calculated from the generated image signal intensity distribution data and illuminance distribution data of the reading surface detected by causing the irradiation unit to emit light in advance.
The chart for creating a scanner profile and the chart for creating a printer profile are different from each other in a structure of a patch, and therefore are different from each other in the degree of an influence by a flare (referred to as flare level). Therefore, in order to utilize a scanner profile created using the chart for creating a scanner profile, it is necessary to correct a flare level of the chart for creating a printer profile (match the flare level of the chart for creating a printer profile with that of the chart for creating a scanner profile).
As a method for correcting this flare level, a method for calculating flare correction data in advance as described in JP 2003-283773 A is considered. However, this method cannot correspond to charts having various patch structures. That is, in order to correspond not only to a fixed chart but also to various charts, it is necessary to correct a flare level dynamically. On the other hand, a method for creating a printer profile by measuring all patches of a chart for creating a printer profile with a colorimetric apparatus without using flare correction data is also considered. However, it takes time to acquire a colorimetric value with the colorimetric apparatus, and many charts have to be output in order to acquire a colorimetric value. Therefore, waste paper is increased disadvantageously.